linux-ppp.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	stable@vger.kernel.org, Eric Dumazet <edumazet@google.com>,
	Paul Mackerras <paulus@samba.org>,
	linux-ppp@vger.kernel.org, syzbot <syzkaller@googlegroups.com>,
	Guillaume Nault <gnault@redhat.com>,
	"David S. Miller" <davem@davemloft.net>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.10 208/563] ppp: ensure minimum packet size in ppp_write()
Date: Mon, 24 Jan 2022 19:39:33 +0100	[thread overview]
Message-ID: <20220124184031.630830705@linuxfoundation.org> (raw)
In-Reply-To: <20220124184024.407936072@linuxfoundation.org>

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 44073187990d5629804ce0627525f6ea5cfef171 ]

It seems pretty clear ppp layer assumed user space
would always be kind to provide enough data
in their write() to a ppp device.

This patch makes sure user provides at least
2 bytes.

It adds PPP_PROTO_LEN macro that could replace
in net-next many occurrences of hard-coded 2 value.

I replaced only one occurrence to ease backports
to stable kernels.

The bug manifests in the following report:

BUG: KMSAN: uninit-value in ppp_send_frame+0x28d/0x27c0 drivers/net/ppp/ppp_generic.c:1740
 ppp_send_frame+0x28d/0x27c0 drivers/net/ppp/ppp_generic.c:1740
 __ppp_xmit_process+0x23e/0x4b0 drivers/net/ppp/ppp_generic.c:1640
 ppp_xmit_process+0x1fe/0x480 drivers/net/ppp/ppp_generic.c:1661
 ppp_write+0x5cb/0x5e0 drivers/net/ppp/ppp_generic.c:513
 do_iter_write+0xb0c/0x1500 fs/read_write.c:853
 vfs_writev fs/read_write.c:924 [inline]
 do_writev+0x645/0xe00 fs/read_write.c:967
 __do_sys_writev fs/read_write.c:1040 [inline]
 __se_sys_writev fs/read_write.c:1037 [inline]
 __x64_sys_writev+0xe5/0x120 fs/read_write.c:1037
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x54/0xd0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Uninit was created at:
 slab_post_alloc_hook mm/slab.h:524 [inline]
 slab_alloc_node mm/slub.c:3251 [inline]
 __kmalloc_node_track_caller+0xe0c/0x1510 mm/slub.c:4974
 kmalloc_reserve net/core/skbuff.c:354 [inline]
 __alloc_skb+0x545/0xf90 net/core/skbuff.c:426
 alloc_skb include/linux/skbuff.h:1126 [inline]
 ppp_write+0x11d/0x5e0 drivers/net/ppp/ppp_generic.c:501
 do_iter_write+0xb0c/0x1500 fs/read_write.c:853
 vfs_writev fs/read_write.c:924 [inline]
 do_writev+0x645/0xe00 fs/read_write.c:967
 __do_sys_writev fs/read_write.c:1040 [inline]
 __se_sys_writev fs/read_write.c:1037 [inline]
 __x64_sys_writev+0xe5/0x120 fs/read_write.c:1037
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x54/0xd0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: linux-ppp@vger.kernel.org
Reported-by: syzbot <syzkaller@googlegroups.com>
Acked-by: Guillaume Nault <gnault@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/net/ppp/ppp_generic.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c
index 33b2e0fb68bbb..2b9815ec4a622 100644
--- a/drivers/net/ppp/ppp_generic.c
+++ b/drivers/net/ppp/ppp_generic.c
@@ -69,6 +69,8 @@
 #define MPHDRLEN	6	/* multilink protocol header length */
 #define MPHDRLEN_SSN	4	/* ditto with short sequence numbers */
 
+#define PPP_PROTO_LEN	2
+
 /*
  * An instance of /dev/ppp can be associated with either a ppp
  * interface unit or a ppp channel.  In both cases, file->private_data
@@ -496,6 +498,9 @@ static ssize_t ppp_write(struct file *file, const char __user *buf,
 
 	if (!pf)
 		return -ENXIO;
+	/* All PPP packets should start with the 2-byte protocol */
+	if (count < PPP_PROTO_LEN)
+		return -EINVAL;
 	ret = -ENOMEM;
 	skb = alloc_skb(count + pf->hdrlen, GFP_KERNEL);
 	if (!skb)
@@ -1632,7 +1637,7 @@ ppp_send_frame(struct ppp *ppp, struct sk_buff *skb)
 	}
 
 	++ppp->stats64.tx_packets;
-	ppp->stats64.tx_bytes += skb->len - 2;
+	ppp->stats64.tx_bytes += skb->len - PPP_PROTO_LEN;
 
 	switch (proto) {
 	case PPP_IP:
-- 
2.34.1




           reply	other threads:[~2022-01-24 20:12 UTC|newest]

Thread overview: expand[flat|nested]  mbox.gz  Atom feed
 [parent not found: <20220124184024.407936072@linuxfoundation.org>]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20220124184031.630830705@linuxfoundation.org \
    --to=gregkh@linuxfoundation.org \
    --cc=davem@davemloft.net \
    --cc=edumazet@google.com \
    --cc=gnault@redhat.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-ppp@vger.kernel.org \
    --cc=paulus@samba.org \
    --cc=sashal@kernel.org \
    --cc=stable@vger.kernel.org \
    --cc=syzkaller@googlegroups.com \
    --subject='Re: [PATCH 5.10 208/563] ppp: ensure minimum packet size in ppp_write()' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).